Rescuers struggle to save some 30 Chinese fishermen whose two boats were wrecked when typhoon Bolaven hit South Korea.

Fishing boats were tied to each at a port in Incheon, west of Seoul, in preparation for Typhoon Bolaven [Reuters]

Rescuers swam through stormy seas to try to save some 30 Chinese fishermen whose two boats were wrecked when a strong typhoon battered South Korea, coastguard officers said.

Officials issued an alert for almost the entire country as Bolaven - the strongest typhoon for almost a decade to hit South Korea - swept towards flood-affected North Korea on Tuesday.

The Chinese boats were hit early on Tuesday after the storm smashed into the southern resort island of Jeju.

Six crew members have so far been pulled to safety by ropes after coastguards and firefighters swam to the wreckage some 50 metres offshore, said a coastguard spokesman at Seogwipo.

"Many people are hanging onto the wreckage of one boat and rescuers are pulling them ashore with ropes," he told the AFP news agency. The other boat was broken in two and sank, he added.

Rescued crew members gave different figures - between 31 and 34 - for the total number of crew aboard the boats Yue Jiang Cheng Yu 91104 and 91105, registered in Weihai city in China's Shandong province.

Power cuts

Scores of flights and ferry services plus schools in Seoul and several other areas were shut on Tuesday as Bolaven approached.

The transport ministry said all 87 sea ferry services had stopped running. A total of 247 flights - 183 domestic and 64 international - have been cancelled since Monday.

The typhoon brought heavy rain and strong winds to southern and western areas of the country, cutting power and bringing down street lights, shop signs and even church spires.

On Jeju, TV footage showed homes with collapsed roofs and uprooted trees. Yonhap news agency said power cuts had hit some 50,000 households on the island as well as more than 70,000 homes in the southwestern province of South Jeolla since Monday night.

The US and South Korean armed forces called a temporary halt to a large-scale joint military exercise that began last week.

The weather service said Bolaven's eye would be over the Yellow Sea, about 200km southwest of Seoul, around noon local time (03:00 GMT). It would come closest to the city two hours later and was expected to move on to hit North Korea at around 6:00 pm (09:00 GMT).

The impoverished North is already struggling to clear up after floods earlier in the summer killed scores of people.Weather officials said Typhoon Tembin was also threatening the Korean peninsula.

It was now about 380km southwest of Taiwan and moving at a speed of 16km an hour. Tembin was forecast to be some 200km west of Jeju early on Friday.